Electrical precipitator



April 18, 1950 w MaGKENZIE 2,504,858

ELECTRICAL PRECIPITATOR Filed Oct. 29, 1946 /NVENTO/? lg /wvezw WMACKENZIE IVE V Patented Apr. 18, 1950 g-Mass, assignor to RaytheonManufacturing Company, Newton, Mass a corporation of DelawareApplication October 29, 1946, Serial No. 706,380

-8 Claims.

This invention relates toelectrical precipitators for separating dust,smoke, and similar impurities from air or other gases. Moreparticularly, the invention relates to electrical .pnecipitators of thetype in which the air or other gas to be purified is first ionized andthereafter passed through a collecting device in which the impuritiesare collected.

in the copending application .of Hans Klemperer, Serial No. 678,155,filedJuneZO, 1946, there is disclosed a precipitator in which theionizing device is energized from .an alternating current source withoutthe necessity of providing rectifiers between the source and theionizing electrodes.

The present invention concerns a construction in which the ionization iseffected in a, smilar manner from the alternating .current source and inwhich advantage is taken of the rectifying property of theionizingdevice to obtain a rectifled voltage for application to thecollecting device.

Accordingly, it is among the objects of the present invention toprovide, in a .precipitator of the type having separate ionizing andprecipitating means, a construction which avoids the necessity ofproviding rectifiers for effecting either ionization or collection ofthe .dust particles.

The above and other objects and features of the invention willbemadefully apparent to those skilled in :the art from a consideration of the.following detailed description taken in conjunction with theaccompanying ,drawing, wherein:

1 illustrates schematically .a circuit in accordance withtheinvention;and

Fig.2 is a time-voltage and time-current graph illustrating theoperationof Fig. 1.

' In Fig. l of the drawing, reference number .13 indicates generally athree phase transformer having Aeconnected primary. windings 1.! andY-connected secondary -.Wihdin-gs .12. The outer. terminals l3, l4, and!5 of theYeconnected sec.- ondary windings l2 are directly connected,respectively, to fine wire electrodes it, H, and I3, which fine wireelectrodes extend transversely through a tubular member I!) of metal orother conductive material providing an air channel. The channel I9constitutes an electrode coacting with each of the fine wire electrodesl6. ll, and I8. Some point 22 on the tubular member is is connectedthrough a resistor 23 to the neutral point .2 5 ofthesecondary windingsl2. The connection between the resistor 23 and the neutral point 24 maybe grounded, as indicated at 25. A collecting device 26, comprising aplurality of alternately charged and ground plates 2'! and 28, isdisposed in the path of vthe gas stream dise char ed fromthe.ionizinadevice, is. In .order to energize the collecting device 26.this device is connected across the resistor 23, the charged 2 plates2'1 being connected at some point between the resistor 23 and the point22 or directly to the tubular member l9 itself. The plates 28 whichalternate with the plates 27 are jointly connected to ground or to thegrounded end of resistor 23;

In operation, it will be understood that the velocity of the air passingthrough the channel I9 is so correlated to the spacing between theelectrodes l6, l7, and I8 that all parts of the air passing through thetubular member 1% are treated by at least one of the electrodes l5, l1,and I8 in the manner disclosed in the copending application previouslymentioned, and that no part of such air remains unionized. The positivepeaks of potential on the electrodes 5, ll, and I8 are synchronized withthe velocity of the air flow, to the end that separate portions of theair will be treated by an ionizing discharge between each electrode andthe common electrode provided by tubular member I9 during the SEC:-cessive positive peaks of potential upon the fine wire electrodes. Thepositive peaks are applied in order It, It, ll, respectively. Althoughthe alternating potential applied to the electrodes :16, ii, and itreverses in polarity, it will be understood ;that conduction is greaterwhen the polarity is in one direction than when it is in the oppositedirection. Thus, when the potential upon any given fine wire electrodehas reached the value at which an ionizingdischarge can occurin the.posi: tive direction, the current fiow is far greater than when thepolarity of the electrodes is reversed. Such a. discharge betweenanelectrode of relatively large area and an electrode of relatively smallarea will be referred to as an asymmetric discharge.

The greater conduction in one direction than in the opposite directionpermits the ionizing means to be utilized as a rectifier, to provide asubstantially constant voltage for energizing the collecting device 26.Thus, due to the unidirecr tional nature of the conductionthrough the"ionizing device, the tubular member l9 may be main tained at a highpotential relative ,to ground, which potential will depend upon thevalue of the resistor 23.,which should be high. Preferably, apotentialdifference of about 12 k. v. willexist between any oneof thefine wire electrodes I6. I l, and I8 and thecommcn electrode 153 duringvthe positive peak of potential upon that electrode. The potential acrossthe plates of collecting device will preferably be of the order of 6 ;k.v.

Referring now to Fig. 2, a sinusoidal curve A illustrates the volta ewave which is applied .by one of the secondary windings between its finewire electrodeand-the tubular member it. -When the ,wire electrodeisposi-tive with respect to the tubularrmember, current begins to flowthrough the resistor 23at a relatively low voltage value,

as is indicated by shaded area B. When the polarity is reversed duringthe succeeding halfcycle of curve A, a relatively higher voltage valuemust be reached before current begins to flow through resistor 23, andtherefore current flows in the reverse direction for a relativelyshorter period of time, as is indicated by shaded area C. Now, collectorassembly 26 is connected across resistor 23, and is, as is well known, acapacitor, due to the interleaved plate construction of plates 21 and28. fore has an average value which is'in one drection, as is indicatedby the straight line D. The secondary voltage values and interelectrodespacings may be so adjusted that shaded area C is reduced substantiallyto the vanishing point. Fig. 2 illustrates only one of the three phases,but it will be readily seen that the other phases have the same effectin the collector assembly.

While there has been herein disclosed a preferred embodiment of theinvention, other embodiments within the scope of the appended claimswill be obvious to those skilled in the art from a consideration of theembodiment shown and the teachings hereof.

What is claimed is:

1. An electrical precipitator comprising a metallic member forming achannel for passing a gas stream and constituting a relatively fiatsurface electrode, at least one electrode of relatively sharp surfacecurvature within said channel, a source of alternating potential forenergizing said electrodes to effect an asymmetric ionizing dischargetherebetween, a plurality of collector plates disposed in the gas streamon the gas discharge side of said ionizing electrodes, means forderiving a unidirectional potential from asymmetric discharge, and meansfor applying the potential so derived across said collector plates.

2. An electrical precipitator comprising a metallic member forming achannel for passing a gas stream and constituting a relatively fiatsurface electrode, a plurality of electrodes of relatively sharp surfacecurvature within said channel, a source of alternating potential forenergizing said electrodes to effect asymmetric ionizing dischargesbetween said large surface electrode and each of said electrodes ofsmall surface area, a plurality of collector plates disposed in the gasstream on the gas discharge side of said ionizing electrodes, means forderiving a unidirectional potential from said asymmetric discharges, andmeans for applying the potential so derived across said collectorplates.

3. An electrical precipitator comprising a metallic member forming a.channel for passing a gas stream and constituting a large surfaceelectrode, at least one fine wire electrode within said channel, asource of alternating potential for energizing said electrodes to effectan asymmetric ionizing discharge therebetween, a plurality of collectorplates disposed in the gas stream on the gas discharge side of saidionizing electrodes, means between said surface electrode and saidsource for deriving a unidirectional potential from said asymmetricdischarge, and means for applying the potential so derived across saidcollector plates.

4. An electrical precipitator comprising a plurality of electrodesbetween which an asymmetric ionizing discharge is adapted to occur andpast which a gas stream may be caused to flow, an alternating currentsource for energizing said The charge on this capacitor thereelectrodes,a plurality of collector plates disposed in the gas stream on the gasdischarge side of said ionizing electrodes, means for deriving aunidirectional potential from said asymmetric discharge, and means forapplying the potential so derived directly across said collector plates.

5. An electrical precipitator comprising an electrode of relatively flatsurface and an electrode of relatively sharp surface curvature betweenwhich an asymmetric ionizing discharge is adapted to occur and pastwhich a gas stream may be caused to flow, an alternating current sourcefor energizing said electrodes, a plurality of collector plates disposedin the gas stream on the gas discharge side of said ionizing electrodes,means for deriving a unidirectional potential from said asymmetricdischarge, and means for applying the potential so derived directlyacross said collector plates,

6. An electrical precipitator comprising a fine wire electrode and asurface electrode between which an asymmetric ionizing discharge isadapted to occur and past which a gas stream may be caused to flow, analternating current source for energizing said electrodes, a pluralityof collector plates disposed in the gas stream on the gas discharge sideof said ionizing electrodes, means for deriving a unidirectionalpotential from said asymmetric discharge, and means for applying thepotential so derived directly across said collector plates.

7. An electrical precipitator comprising a plurality of fine wireelectrodes, a surface electrode coacting with each of said fine wireelectrodes to produce an asymmetric ionizing discharge, means includingin part said surface electrode for passing a gas stream past saidelectrodes, an alternating current source for energizing saidelectrodes, a plurality of collector plates disposed in the gas streamon the gas discharge side of said ionizing electrodes, means forderiving a unidirectional potential from said asymmetric discharge, andmeans for applying the potential so derived directly across saidcollector plates.

8. An electrical precipitator comprising a fine wire electrode and asurface electrode between which an asymmetric ionizing discharge isadapted to occur and past which a gas stream may be caused to flow, analternating current source for energizing said electrodes, a pluralityof collector plates disposed in the gas stream on the gas discharge sideof said ionizing electrodes, means between said surface electrode andsaid source for deriving a unidirectional potential from said asymmetricdischarge, and means for applying the potential so derived directlyacross said collector plates.

KENNETH W. MACKENZIE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,343,285 Schmidt June 15. 19201,389,126 Chubb Aug. 30, 1921 2,142,129 Hoss Jan. 3, 1939 2,295,152Bennett Sept. 8, 1942 FOREIGN PATENTS Number Country Date 682,588Germany c Oct. 18, 1939

